Electric circuit breaker

ABSTRACT

An electric circuit breaker has movable and stationary contacts which are operable automatically as well as manually. The movable contact is separated from the stationary contact by electromagnetic repulsion generated therebetween when there occurs a short circuit in the load circuit of the circuit breaker, causing the switching mechanism of the contacts positively to be collapsed independently of its automatic releasing device.

[[22 Filed:

United States Patent Iida et al.

541 ELECTRIC CIRCUIT BREAKER [72] Inventors: Masachika lida; Yasutaka Irnajyo, both of Tokyo, Japan [73] Assignee: j'lokyo Shibaura Electric Co., Ltd.,

v Kawasaki-shi, Japan Nov. 5, 1969 [211 Appl. No.: 874,244

[52] U.S. Cl ..-.335/l6, 335/195 [51] Int. Cl. .110! 77/02 [58] Field oisearch ..335/l6, 195; 337/71 X, 59

[56] References Cited 7 UNITED STATES PATENTS 2,345,105 3/1944 Dorfman et a1. ..337/71 X [4 1 Feb. 29, 1972 2,600,223 6/1952 Dorfman et al ....337/59 3,244,837 4/1966 Strobe! 337/71 X 3,080,462 3/1963 Casey ....335/16 3,505,622 4/1970 Strobe] ..335/l6 Primary Examiner1-1arold Broome Attorney-Irving M. Weiner [5 7] ABSTRACT An electric circuit breaker has movable and stationary contacts which are operable automatically as well as manually.

The movable contact is separated from the stationary contact by electromagnetic repulsion generated therebetween when there occurs a short circuit in the load circuit of the circuit breaker, causing the switching mechanism of the contacts positively to be collapsed independently of its automatic releasing device.

1 Claim 5 Drawing Figures PAIENTEDFEB 29 I972 SHEET 1 [1F 4 PATENTEDFEBES I972 SHEET3UF4 FIG. 3

F 54 o 35 O 3 1 O k Ill! ELECTRIC CIRCUIT BREAKER BACKGROUND OF THE INVENTION Thisinvention relates to an electric circuit breaker and more pa'rticularlyto an electric circuit breaker, wherein there are received ina casing made of insulating material manually and automatically operable contacts together with their operatingmechanism.

As is well known, such breaker serves as a circuit protecting device, the operating mechanism of which includes a toggle mechanism and a trip lever, where the load circuit of the breaker is in'a normal state, the trip lever is set at an interlocked position by a thermally and electromagnetically releasing device. However, where there flows an overcurrent through the circuit breaker, the releasing device releases the trip lever due to its inverse time-current characteristics defined by the value of current, collapsing the toggle mechanism to open the contacts, so that the circuit is saved from an overloaded condition. Such function also arises where there occurs a'dead' short in the load circuit, In this case the trip lever is electromagnetically released in a moment and the breaker opens the load circuit to remove the fault quickly.

'Howevenelimination of the short circuit naturally leads toan undesired time delay, which is caused due to a certain length of time'bein'g required in the collapsing of the linkmechanism. The duration of said delay depends on the number of points at which the links are connected together. Thus, the time interval from the initial trip to the opening of the contacts substantially runs from 7 to m.sec. Further, there is consumed a period of about 10 m.sec. in extinguishing a high-energy are drawn across the separated contacts. As a result, the total time to'effect full interruption substantially amounts to m.sec.,

allowing 'a'short circuit current to pass during'an interval between two sequential peaks of the commercial frequency.

Accordingly,'there are only applied to the load circuit so great electromagnetic stresses and thermal shocks as to destroy it, but also the breaker itself is adversely affected by the high energyand temperature of the are which prevails between the separatedcontacts. Besides, the failure of the releasing device would render the circuit breakerincapable of interrupting any fault in the load circuit, leading to its eventual destruction.

SUMMARY OF THE INVENTION It is accordingly an object of the present invention to provide a circuit breaker which is free from the aforementioned drawbacks'and capable of being reliably used.

Another object of the invention is to provide a circuit 'breakerwherein, when there occurs a short circuit in the load circuit, contacts are instantly opened by electromagnetic repulsion-acting therebetween, thereby reducing a time delay resulting from the collapsing of the operating mechanism to so invention'comprises separable contacts which are manually and automatically operable, an operating mechanism for bringing one of the contacts from the open to the closed positionor vice versa and a device for automatically releasing the operating mechanism for its collapsion and causing the first mentioned contact to be separated from the other according to the magnitude of a prescribed high current flowing through the circuit breaker. The circuit breaker is provided with a relatively elongated movable arm supporting at one of its ends the first mentioned contact and also with a relatively elongated stationary barfor supporting atone of its ends the othercontact. Said armand bar are made to overlap each other in the longitudinal direction with a clearance left therebetween'soas to form a loop for allowing the passage of a load current. There is also installed a means whereby, whenthere flows' an overcurrent through said loop, the operating mechanism is collapsed independently of the releasing device by themovablearm which is separated from the stationary bar byelectromagnetic repulsion generated therebetween at that time.

BRIEF EXPLANATION OF THE DRAWINGS FIG. 1 is a side view of a circuit breaker according to an embodiment of thepresent invention with the sidewall of the cats ing broken away to indicate the internal parts;

FIG. 2 is a similar side view to FIG. 1 showing the initial movement of the movable arm when separated from the stationary bar due to electromagnetic repulsion acting therebetween;

FIG. 3 is a side view of the circuit breaker presenting the operating'mechanism collapsed by the movable arm;

FIG. 4 is aside view of the circuit breakershowing the trip lever released from the catch member of the releasing device;

and

FIG. 5 is a fractional side view of another embodiment of the invention.

DETAILED DESCRIPTION OFTHE INVENTION Referring to FIG. 1, the circuit breaker of the present invention is provided with a casing 10 made of insulating material including the body 11 of the-circuit breaker and a cover 12. On the base of the body 11 is fixed a conductor 13, one end-of which terminates at a source terminal 14 and the other end of which is bent atan intermediate point on said bottom in parallel relationship with the unbent portion to form a stationary bar 15 having a predetermined length, to the furthest'end of which is fitted a stationary contact 16.

A Y-shaped member 17 having aleg l8 and two branches l9 and-2 0 is pivotally supported by a pin 21 fixed to'thebody 1 l. A movable contact arm 22 is pivotally fitted to the'branch l9 by'a pin 23 penetrating said branch 19 and carries-atthe end a contact 24 which makes and breaks with respect to the contact 16 of the stationary bar 15. The movable contact-arm 22 is so disposed that when the contacts l6'and 24 are'allowed to make, the bottom surface of the movable contact -arm22 andthe upper'surface of the bar 15 are superposed on each other with a relatively narrow clearance allowed over a predetermined length. Around the pin 23 is wound a torque spring 27a, one end 'of which is engaged with the upper part-of the movable arm 22 and the other with the pin 21. Thus the movable arm 22 is normally biased by the spring 27a in a clockwise direction to apply asuitable contact pressure to the surfaces of the contacts -24 and 16. The clockwise movement of the movable arm 22 is limited by allowing its rearshoulder portion 26 to be engaged with the latch porfion of the branch 20 of the Y-shaped member 17. Accordingly, when the break operation is completed, the movable contact '24 is fully separated from the stationarycontact 16 as indicated by the dotted lines of FIG. 1. For the later described'operation, there is formed integrally with the movable contact arm 22a-projection 27 extending upward fromthe back thereof. There is provided a flexible lead 28, one end of which is electrically'connected to the movable contact arm 22 and the other end of which is also electrically connected through a U-shaped conductor 29 toa load terminal 30 disposed at the base of the easing 10.

To bring the movable contact arm 22' from the open tothe closed position or vice 'versa, there is set up a mechanism generally designated by a numeral 31 which comprisesa pair of links 32 and 33 constituting a toggle linkage. One end of the link 32 is pivotally fitted to the pin 23 supporting the movable contact arm 22 and the other end to one end of the -link 3 3 'by a pin 34 to-form a toggle knee. The pin-34 of the toggle kneeis positionedclose by the-left side of the upper end of theprojection 27 of the movable contact arm 22. The other end of the link 33 is pivotally fitted by a pin 36 to the intermediate position of a trigger lever 35 in its longitudinal direction. Further, one end of the trigger lever is pivotally supported by a pin 37 and the other end is engaged with a releasing device generally designated by a numeral 38.

For the manual switching operation of the movable contact arm, there is provided a handle 39 projecting from the casing cover 12. To the prescribed position in the casing is pivotally disposed a support member, though not shown to simplify the illustration, to the top of which there is fitted said handle 39. To bring the toggle linkage from the set to the collapsed position or vice versa by a snapping action, there is stretched a coiled tension spring 40 between the handle 39 and the pin 34 of the toggle knee. Where the trigger lever 35 is engaged with the releasing device 38, then the movement of the handle 39 to the indicated position allows the central line of the spring 40 to pass the position of the pin 36 of the link 33 and in consequence the toggle linkage causes the links 32 and 33 to be set. Thus, the Y-shaped member 17 is pushed downward clockwise by the spring 40 acting on the toggle linkage, causing the movable contact arm 22 to rotate about the pin 23 and the contacts 16 and 24 to be engaged each other. Conversely, where the handle 39 is transferred form the indicated position through the pin 36 to the left end, then the toggle linkage is collapsed by the tension of the spring 40, allowing the contacts 16 and 24 to be immediately separated from each other.

There is further provided an arc extinguishing device, for example, deionizing grids, which operate, as is generally known, in such a-manner as to draw out the are initiated across the separated contacts 16 and 24 and break it up into a plurality of shorter arcs for cooling and extinguishment.

An automatic releasing device 38 comprises a latch 42 pivotally supported by a pin 43 and two legs 44 and 45 extending downward therefrom. This releasing device 38 involves a bimetallic strip 46 which is fixed at the bottom end to the U- shaped conductor 29 and extends upward along one of the legs of the U-shaped conductor 29 so as to be heated thereby. At the upper end of the bimetallic strip 46 is positioned an adjusting screw 47 facing the leg 44 through an adjustable gap so as to allow the circuit breaker to adjust the prescribed inverse time-current characteristics according to the magnitude of the overcurrent expected. When there flows through the circuit breaker an overcurrent having a prescribed value, then the bimetallic strip 46 is strained to allow the leg 44 to be pushed by the screw 47, the latch 42 to rotate about the pin 43 anticlockwise and in consequence the trip lever 35 to be released from the latch 42 with the previously described time delay. The trip lever 35 rotates clockwise about the pin 37 by the force of the spring 40 transmitted through the link 33 to allow the pin 36 to be shifted beyond the central line of the spring 40, so that the movable contact arm 22 is separated from the stationary bar 15 by collapsing of the toggle linkage and interrupt the load circuit. The automatic releasing device also comprises a C-shaped magnetic pole member 48 titted to the periphery of one of the legs of the U-shaped conductor 29. The poles of said magnetic member 48 face through a gap a movable armature 49 pivotally supported by a pin 50. The movable armature is engaged at the upper end with the leg 45 of the latch 42 and is normally biased by a bias spring 51 so as to allow the lower part to be separated from said poles. Numeral 52 designates as adjustable screw, at the lower end of which is disposed a cam plate 53 engaged with the leg 45 of the latch 42 through the upper part of the armature 49. When the screw 52 rotates, the cam plate 53 also rotates, varying the degree of engagement between the latch 42 and trigger lever 35 and the length of the clearance between the magnetic pole member 48 and armature 49, whereby the automatic releasing device can operate in response to an extremely large current having a desired value due to the electromagnetic release of the trigger lever 35.

rent through a loop comprising the movable contact arm 22, contacts 24 and 16 and stationary bar 15, allowing the loop to extend itself due to an electromagnetic force generated therein. Since the stationary bar 15 is immovable, the movable contact arm 22 rotates anticlockwise against the force of the bias spring 27a. Said arm 22 is separated at an extremely high speed independently of the disengagement of the trigger lever 35 by the automatic releasing device 38. FIG. 2 presents the initial stage of said separation. The moment the movable contact arm 22 begins to be disengaged, the projection 27 urges the toggle knee or pin 34 leftward immediately to collapse the toggle linkage involving a pair of links 32 and 33. FIG. 3 shows the final position of all the switching mechanism collapsed by the electromagnetic repulsion action between the movable contact arm22 and stationary bar 15. This final position is retained, even though the release of the trigger lever 35 by the releasing device 38 is not connected. According y, any problem associated with the failure of the releasing device 38 need not be taken into consideration. Generally, however, the pole member 48 attracts the armature 49 in an extremely short time, so that the release of the trigger lever 35 due to magnetic attraction is started substantially at the same time the toggle linkage begins to be collapsed by the striking of the toggle knee by the movable contact arm 22 separated from the stationary bar 15 by electromagnetic repulsion. Where the releasing device 38 does not fail, the parts of the circuit breaker which have been fully released and collapsed assume the positions shown in FIG. 4.

To reset the collapsed mechanism, the handle 39 is moved to the right and a latch, not shown, attached to the handle 39 is engaged with the shoulder 54 of the trigger lever 35. Then the trigger lever 35 is transferred to the left to have its end engaged with the latch 42 of the releasing device 38.

According to another embodiment of FIG. 5 in which the same parts as those of the aforementioned embodiment are designated by the same numerals, the movable contact arm 22 circuit of the breaker, then there flows an extremely great curhas a lug or pin 55 engaged with the link 32 so as to collapse the toggle linkage 31. Since the embodiment of FIG. 5 operates in the same manner as the preceding one, description thereof is omitted.

According to the circuit breaker of the present invention, when there occurs a short circuit in the load circuit, the toggle linkage is collapsed positively and quickly without the aid of the releasing device by the movable arm separated from the stationary bar due to electromagnetic repulsion acting therebetween, so that the circuit breaker never fails to carry out interruption. Further, the instant separation of contacts due to electromagnetic repulsion allows the time required in fully releasing them to be far more reduced than that used in the complete collapsing of the toggle linkage, thus rendering the time delay of the mechanically movable parts of the circuit breaker substantially negligible at the time of interruption. Accordingly, the circuit breaker by the present invention effects the interruption of the shorting of its load circuit only in about half the time which is generally consumed by the prior art circuit breaker. Since such short circuit is eliminated from the load circuit before it grows large, the circuit breaker is effectively saved from being damaged. This also permits a circuit breaker used in a circuit involving a large load capacity to have an increased interrupting capacity.

It has also been disclosed that the interrupting capacity of a circuit breaker can be elevated by molding a casing from unsaturated polyester containing aluminum hydroxide as a main filler, and that this molded casing has a more excellent arcproof property than an ordinary casing made of phenolic resin.

What is claimed is:

1. In an electric circuit breaker provided with separable contacts capable of being operated automatically as well as manually, an operating mechanism including a toggle knee for bringing one of the contacts to the closed and open positions as required, and a device for automatically releasing and collapsing the operating mechanism so as to separate the firstmeans for collapsing said operating mechanism independently of the releasing device by the movable arm separated from the stationary bar due to electromagnetic repulsion generated in said loop when there is introduced an overcurrent therethrough; and

said means for collapsing the operating mechanism including a movable arm having a projection integrally formed therewith for striking said toggle knee of said operating mechanism. 

1. In an electric circuit breaker provided with separable contacts capable of being operated automatically as well as manually, an operating mechanism including a toggle knee for bringing one of the contacts to the closed and open positions as required, and a device for automatically releasing and collapsing the operating mechanism so as to separate the first-mentioned contact from the other according to the magnitude of a prescribed high current flowing through the circuit breaker, the combination comprising: a relatively elongated movable arm for supporting the firstmentioned contact at one of its ends; a relatively elongated stationary bar for supporting the other contact at one of its ends; said arm and bar being so arranged as to overlap each other in a longitudinal direction with a clearance left therebetween to form a loop through which there flows a load current; means for collapsing said operating mechanism independently of the releasing device by the movable arm separated from the stationary bar due to electromagnetic repulsion generated in said loop when there is introduced an overcurrent therethrough; and said means for collapsing the operating mechanism including a movable arm having a projection integrally formed therewith for striking said toggle knee of said operating mechanism. 